It is well established that alcohol use and smoking behavior are highly correlated, particularly for individuals who are moderate to heavy drinkers, as compared to light drinkers. In general, smokers are more likely to drink regularly and consume larger quantities of alcohol than nonsmokers and drinkers are much more likely to smoke. However, much is still unknown concerning the interaction of the two substances. Human laboratory studies examining interactions of nicotine and fixed-doses of alcohol have demonstrated alterations in craving, subjective intoxication, and mood. Investigations have yet to examine the effect of nicotine, administered by transdermal nicotine patch, on reactivity to alcohol. Prior studies have examined nicotine nasal spray and nicotine gum on reactivity to a fixed-dose of alcohol but is possible that the pharmacokinetics and blood nicotine levels achieved by transdermal patch may alter findings produced by other routes of administration. Additionally, research has yet to examine the effect of transdermal nicotine replacement on alcohol self-administration behavior. Given that transdermal nicotine replacement is the most commonly used nicotine replacement strategy, it effects on alcohol reactivity is an important area of investigation. Using an alcohol self-administration paradigm developed by our group, the primary aim of this project is to examine whether transdermal nicotine replacement (21 mg/day), as compared to mild nicotine withdrawal (0mg placebo patch), alters reactivity to alcohol following exposure to a priming drink and subsequent ad-libitum drinking in individuals who are moderate to heavy drinkers. Specifically we will examine whether nicotine replacement reduces 1) ad-libitum alcohol consumption, 2) alcohol craving, 3) subjective intoxication, and 4) mood. A secondary aim is to examine whether transdermal nicotine replacement decreases the ability of alcohol to prime tobacco craving. This study will have important implications for alcohol-nicotine interactions, smoking cessation in alcohol drinkers, and alcohol challenge studies in general.